Method, Apparatus and Computer Program for Cell Search

1. A method of cell search for a cellular communication device capable of operation in a normal coverage mode and in an extended coverage mode, wherein the method comprises: retrieving a first list of frequencies for cell search comprising at least one frequency item; searching for cells using the frequency items of the first list in consecutive order until either a cell, which enables connection in the normal coverage mode, is found or the first list is exhausted; and if a cell is found which enables connection in the normal coverage mode, connecting to said cell for operation in the normal coverage mode; or if the first list is exhausted, retrieving a second list of frequencies, searching for cells using the frequency items of the second list in consecutive order until either a cell is found which enables connection in the extended coverage mode or the second list is exhausted, and if a cell is found which enables connection in the extended coverage mode, connecting to said cell for operation in the extended coverage mode.

2. The method of claim 1 , comprising: if the second list is exhausted, retrieving a third list of frequencies and a different setting for the extended coverage mode, searching for cells using the frequency items of the third list in consecutive order until either a cell is found which enables connection in the extended coverage mode with the different setting or the third list is exhausted, and if a cell is found which enables connection in the extended coverage mode, connecting to said cell for operation in the extended coverage mode with the different setting.

3. The method of claim 2 , wherein the second and third lists of frequencies are idem.

4. The method of claim 1 , wherein if the second list is exhausted, aborting cell search.

5. The method of claim 1 , wherein the first and second lists of frequencies are idem.

6. The method of claim 1 , comprising, prior to searching for cells using the frequency items of the first list in consecutive order until either a cell is found which enables connection in the normal coverage mode, searching for cells using the frequency items of the first list in consecutive order until a cell is found which enables connection in the extended coverage mode and connecting to said cell for operation in the extended coverage mode, and then continuing with the searching for cells using the frequency items of the first list in consecutive order until either a cell is found which enables connection in the normal coverage mode or the first list is exhausted.

7. The method of claim 6 , further comprising determining a cell search criterion, wherein the searching for cells using the frequency items of the first list in consecutive order until a cell is found which enables connection in the extended coverage mode and connecting to said cell for operation in the extended coverage mode is performed conditionally depending on the cell search criterion.

8. The method of claim 7 , wherein the cell search criterion comprises whether a time since connection operation to a cell which serves the cellular communication device or on which the cellular communication device is camping exceeds a threshold, and the searching for cells using the frequency items of the first list in consecutive order until a cell is found which enables connection in the extended coverage mode and connecting to said cell for operation in the extended coverage mode is omitted if the time exceeds the threshold.

9. The method of claim 7 , wherein the cell search criterion is comprised in system information of the cell which serves the cellular communication device or on which the cellular communication device is camping transmitted to the cellular communication device, wherein the searching for cells using the frequency items of the first list in consecutive order until a cell is found which enables connection in the extended coverage mode and connecting to said cell for operation in the extended coverage mode is omitted when the system information so indicates.

10. The method of claim 1 , wherein the frequency items of the list or lists are based on history of earlier connections to cells.

11. The method according to claim 10 , wherein the history of the earlier connections to a cell include frequencies that have been used in the earlier connections to the cell.

12. The method according to claim 10 , wherein the history of the earlier connections to a cell include frequencies that have earlier been signalled to the cellular communication device as part of system information or a dedicated message.

13. The method of claim 1 , wherein the frequency items of the list or lists are pre-stored in the cellular communication device or in a device associated with the cellular communication device.

14. A cellular communication device capable of operation in a normal coverage mode and in an extended coverage mode and comprising: a transceiver; and a cell searcher mechanism arranged to control the transceiver upon cell searching to tune to different frequencies and detect whether respective cells provide appropriate signal properties; and determine a cell for connection for operation in the normal coverage mode or the extended coverage mode, wherein the cell searcher mechanism is further arranged to operate according to a method of cell search for a cellular communication device capable of operation in a normal coverage mode and in an extended coverage mode, wherein the method comprises: retrieving a first list of frequencies for cell search comprising at least one frequency item; searching for cells using the frequency items of the first list in consecutive order until either a cell, which enables connection in the normal coverage mode, is found or the first list is exhausted; and if a cell is found which enables connection in the normal coverage mode, connecting to said cell for operation in the normal coverage mode; or if the first list is exhausted, retrieving a second list of frequencies, searching for cells using the frequency items of the second list in consecutive order until either a cell is found which enables connection in the extended coverage mode or the second list is exhausted, and if a cell is found which enables connection in the extended coverage mode, connecting to said cell for operation in the extended coverage mode.

15. The cellular communication device according to claim 14 , wherein the cellular communication device is a mobile telephone, a cellular modem, or an equipment comprising a cellular modem.

16. The cellular communication device according to claim 15 , wherein the equipment comprising a cellular modem is a machine-type communication, MTC, device.

17. A non-transitory computer-readable storage medium comprising computer-executable code with program instructions, which when executed on a processor of a cellular communication device causes the cellular communication device to perform a method of cell search for a cellular communication device capable of operation in a normal coverage mode and in an extended coverage mode, wherein the method comprises: retrieving a first list of frequencies for cell search comprising at least one frequency item; searching for cells using the frequency items of the first list in consecutive order until either a cell, which enables connection in the normal coverage mode, is found or the first list is exhausted; and if a cell is found which enables connection in the normal coverage mode, connecting to said cell for operation in the normal coverage mode; or if the first list is exhausted, retrieving a second list of frequencies, searching for cells using the frequency items of the second list in consecutive order until either a cell is found which enables connection in the extended coverage mode or the second list is exhausted, and if a cell is found which enables connection in the extended coverage mode, connecting to said cell for operation in the extended coverage mode.

18. A method of a network node for managing cell search of a cellular communication device capable of operation in a normal coverage mode and in an extended coverage mode which is served by or camping on a cell operated by the network node, wherein the method comprises: determining whether the cellular communication device operates in extended coverage mode, wherein, if the cellular communication device operates in extended coverage mode, the network node transmits a signal to the cellular communication device comprising system information prompting the cellular communication device to retrieve a first list of frequencies for cell search comprising at least one frequency item and search for cells using the frequency items of the first list in consecutive order until either a cell, which enables connection in the normal coverage mode, is found or the first list is exhausted, and if a cell is found which enables connection in the normal coverage mode, connect to said cell for operation in the normal coverage mode.

19. A network node capable of managing cell search of a cellular communication device capable of operation in a normal coverage mode and in an extended coverage mode which is served by or camping on a cell operated by the base station, wherein the network node comprises a processor to cause the network node to: determine whether the cellular communication device operates in extended coverage mode, if the cellular communication device operates in extended coverage mode, transmit a signal to the cellular communication device comprising system information prompting the cellular communication device to retrieve a first list of frequencies for cell search comprising at least one frequency item and search for cells using the frequency items of the first list in consecutive order until either a cell, which enables connection in the normal coverage mode, is found or the first list is exhausted, and if a cell is found which enables connection in the normal coverage mode, connect to said cell for operation in the normal coverage mode.